Paid from money donated to Wikipedia – unlike the Google executive. I think it is normal and legitimate for donors to Wikipedia – whether they've donated labour or money – to have a qualitatively different kind of interest in the former case than the latter.

People seem to have a weird expectation that if you want to work on something useful you should expect to be paid well below market rates. (In this case, 50-70% below market!)

Why? I can think of no system of ethics that says someone working on addictive mobile games should be making more than the CEO of wikipedia, but that's exactly what's happening. And still people are mad about it! Apparently suckers who want to do something nice for society should do it for free.